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Ann Saudi MedAnn Saudi MedAnnals of Saudi Medicine0256-49470975-4466King Faisal Specialist Hospital and Research Centre 2771099110.5144/0256-4947.2016.367asm-5-367ImagesIdentification of gout in unusual sites by dual energy computed tomography Xu Suqing Li Fen Xie Xi http://orcid.org/0000-0002-9296-2324From the Department of Rheumatology, The Second Xiangya Hospital, Central South University, Changsha, ChinaCorrespondence: Dr. Xi Xie, Renmin Road No. 139, Changsha, Hunan, China 410011, T: 86 0731 85295255, mecca0000@163.comSep-Oct 2016 36 5 367 368 Copyright © 2016, Annals of Saudi Medicine2016This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
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A 41-year-old man presented with 2-year history of episodic swelling and pain in the knees. He had been initially diagnosed as having gout at a local hospital and treated with allopurinol and diclofenac. The symptoms progressed and he was referred to our department. He denied a history of other diseases. Physical examination found swelling and tenderness in both knees and the right ankle. A joint aspiration from the right knee on admission found sodium urate crystals in the aspirated fluid under a polarized light microscope. Additionally, an abnormal chest radiograph revealed a bone erosion in the left clavicle region. Bone scintigraphy after 99mTc-methylene diphosphonate (99mTc- MDP) injection showed collective radionuclide in both knees, the right ankle, and the first left rib. Bence-Jones protein in the blood and urine were within the normal reference range. To exclude malignancy on the ribs, a dual energy computed tomography (DECT) was performed, which confirmed urate deposits bilaterally in 1 to 4 ribs, extremitas sternalis clavicularis, extremitas acromialis clavicularis, shoulder blades, presternum and cervical vertebra (Figure 1) and both knees (Figure 2). The joints most commonly involved in gout are knees, meta-tarsophalangeal joints (MTPs), and ankles.1 Ribs, clavicle, sternum, scapula and vertebrae are rarely affected. In this case, all of these unusual sites were included. DECT is an imaging advance in recent years showing a high sensitivity and specificity to gout crystals.2 It is useful in differentiating gout from other lesions, such as malignant tumor. Additionally, DECT can identify and color-code monosodium urate crystals in multiple joints simultaneously and noninvasively.3 Considering its high price and the potential risk of radiation, DECT is not a routine tool in gout diagnosis, but it is still highly recommended and is especially useful in scanning and identifying gout in unusual sites, which are hard to differentiate by conventional radiography or nuclear medicine.

Conflict of interest

The authors report no conflict of interest

Figure 1 DECT demonstrated the urate crystal deposition (shown in green) in the ribs, scapula, sternum and cervical vertebra.

Figure 2 DECT demonstrated the urate crystal deposition (shown in green) in the knees.
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REFERENCES
1 Choi HK  Al-Arfaj AM  Eftekhari A    Dual energy computed tomography in tophaceous gout Annals of the rheumatic diseases 2009 68 1609 12 19066180 
2 Glazebrook KN  Guimaraes LS  Murthy NS    Identification of intraarticular and periarticular uric acid crystals with dual-energy CT: initial evaluation Radiology 2011 261 516 24 21926378 
3 Bacani AK  McCollough CH  Glazebrook KN    Dual energy computed tomography for quantification of tissue urate deposits in tophaceous gout: help from modern physics in the management of an ancient disease Rheumatology international 2012 32 235 9 20016988